Hi Paul > > It got a bit garbled in transmission, not sure what this character > > might have been: → > >Keith looks like the mystery garble should have been an arrow or >gives/yields.
Um, yes. Duh! I don't mind admitting it all looks like fly-shit to me. Well, not quite, I can follow it up to a point but easily get lost. Should've guessed the arrows though. >ie : 2 Cl -- ---> Cl2 (gas) + 2 e -- (electrons) >Whether the arrows are oneway or two way I'm not sure in all cases. >Then below should read > > > ... Consider the electrolysis of a water solution of sodium chloride > (common table salt). At the anode the product is, as one might > expect, chlorine gas. > > anode : > 2 Cl -- ---> Cl2 (gas) + 2 e -- (electrons) > > Bubbles of hydrogen form at the cathode; the solution immediately > surrounding this electrode becomes strongly basic. This evidence > indicates that a water molecule rather than a sodium ion is being > reduced : > > cathode : > 2 H2O + 2 e -- ---> H2 (g) + 2 OH -- > > It appears that the water molecule is more readily reduced than the > Na+ ion. This is entirely reasonable when you consider the addition > of sodium metal to water results in the spontaneous reaction : > > 2 Na (solid) + 2 H2O ---> 2 Na+ + H2 (g) + 2 OH -- > > Thus, one can then argue that any sodium ions produced by > electrolysis would immediately react with water to produce H2 >molecules and OH -- ions so the net reaction is that listed for the > cathode. > > To obtain the overall reaction for the electrolysis of a water > solution of sodium chloride, combine the anode and cathode reactions > to give : > > 2 Cl -- + 2 H2O ---> Cl2 (gas) + H2 (gas) + 2 OH -- > > One effect of this cell reaction is the replacement of the chloride > ions originally present by an equal number of hydroxide ions. > Consequently, evaporation of the solution remaining after > electrolysis yields a residue of sodium hydroxide: > > electrolysis : > 2 Cl -- + 2 H2O ---> Cl2 (g) + H2 (g) + 2 OH -- > > evaporation : > 2 Na+ + 2 OH -- ---> 2 NaOH (solid) > > > --------------------------------------------------------------- > > 2 Na+ + 2 Cl -- + 2 H2O ---> 2 NaOH (s) + Cl2 (g) + H2 (g) > > The greater part of the sodium hydroxide and almost all the chlorine > made is prepared by the electrolysis of aqueous sodium chloride; > hydrogen is an important by-product. > > In electrolytic oxidation the number of electrode materials (anode) > is more limited than in reduction processes. Since, in general, it > is important that the anode should be attacked as little as possible > during electrolysis, we are confined to the use of platinum, iridium, > palladium, carbon, iron, and nickel for processes that take place in > alkaline solution, and to the platinum metals and carbon for those > carried out in acid solution. Anodes of lead dioxide may be employed > in sulfuric acid solutions. Of these anodes, iron and nickel have > the lowest oxygen over-voltages. For general work, the most suitable > anodes are: (1) lead, for sulfate solutions; (2) Acheson graphite, > for chloride solutions; and (3) pure nickel or a high-nickel steel > for alkaline solutions. > > >If memory serves me right (which is less often these days) in the commercial >process mercury is used for one of the electrodes. It runs beneath a molten >bath of sodium chloride. As the sodium is formed it dissolves in the >mercury. The mercury is circulated through the cell and into another >reaction vessel where water is added to the mercury. The sodium metal forms >sodium hydroxide and hydrogen with the water. That doesn't sound very kitchen-friendly Paul. Maybe there isn't a kitchen-friendly way, eh? Wood-ash KOH then I guess. Best wishes Keith >Regards Paul. ------------------------ Yahoo! Groups Sponsor ---------------------~--> 4 DVDs Free +s&p Join Now http://us.click.yahoo.com/pt6YBB/NXiEAA/MVfIAA/FGYolB/TM ---------------------------------------------------------------------~-> Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Biofuels list archives: http://archive.nnytech.net/ Please do NOT send Unsubscribe messages to the list address. To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
